An ellipsometry study of silica nanoparticle layers at the water surface

Abstract

We have studied silica nanoparticle layers spread at the air-water interface. The surface pressure of the layers has been determined in a Langmuir trough via two orthogonal Wilhelmy plates. We observed significant differences in surface pressure according to the preparation protocol: layers spread then compressed or layers obtained after successive spreading steps. We also studied the two types of layers by multiple angle of incidence ellipsometry. We introduce a two-layer model which enables us to evaluate the radius of interfacial aggregates and their contact angle with the air-water interface.

Influence of the contact angle of silica nanoparticles at the air–water interface on the mechanical properties of the layers composed of these particles

“…The contact angle increases with an increasing degree of silanization. It has been shown recently that ellipsometry allows in situ measurements of adsorbed particles [13] and leads to similar values of θ to those in ref. 8.…”

“…Although the layer properties depend upon the preparation method, it has been shown that the layers deposited on a clean water surface without being subsequently compressed are similar to the layers adsorbed from the particle dispersions used to generate the foams [13]. In this paper, we extend the previous study of deposited layers of the particles that give the most stable foams (θ ~ 90°) [16], investigating particles exhibiting both larger and smaller contact angles.…”

“…We used an ultrasonic probe (Ultrasonic Processor) operating at 20 kHz with an amplitude of 45% of the maximum in order to have a stable dispersion and to avoid the formation of particle aggregates. The hydrodynamic radius R h of the particles in the dispersion has been measured by dynamic light scattering [13]. Upon increasing x, R h decreases from 87 nm to 72 nm.…”

Plasmonic Ruler at the Liquid–Liquid Interface

“…Furthermore, fluorescence loss induced by photobleaching and fluorescence recovery after photobleaching on the same system revealed that the lateral diffusion of these assemblies is 4 orders of magnitude slower than its bulk counterpart. 36 Second harmonic generation, 37 surface plasmon resonance 38 and ellipsometry 39 have also been shown as a characterization method for NPs at the LLI. More recently, freezefracture shadow-casting cryo SEM has been performed with single-particle resolution of these assemblies.…”

Wrinkling in the deflation of elastic bubbles

“…However, the literature provides many examples of layers buckling before this zero tension state is reached. For example, interfaces coated with spherical [11] and ellipsoidal [12] colloidal particles buckle upon compression whilst the interfacial tension is still a significant fraction of its value before coating. Although commonly observed, the buckling of layers with finite shear modulus has yet to be fully understood from a theoretical point of view.…”